Lead zirconate titanate (PZT) thin films were fabricated using sol-gel spin-coating onto Pt/glass, Pt/Ti/glass and Pt/Ti/$SiO_2$/Si substrates and heat treated using rapid thermal annealing (RTA). The preferred orientation and the perovskite phase content of the PZT thin films were studied using X-ray diffraction analysis (XRD), and the polarization vs electric field (P-E) hysteresis characteristics were investigated using a standardized ferroelectric test system. All of the resulting fims on platinized substrate with Ti adhesion layer were crystallized with the perovskite phase. A preferred (111) orientation was obtained on the Pt/Ti/glass substrate. The saturation polarization of the PZT film on glass substrates was higher than that on Si substrates.
A method and a mechanism for controlling the crystal orientation of PZT thin films have been studied. The PZT thin films were fabricated using sol-gel spin-coating onto Pt/Ti/glass substrates. The films were heat treated at the temperature ranging from 270 to 350℃ for pyrolysis. The firing for crystallization was applied at 650℃ using rapid thermal annealing (RTA) for 1 min. Then the films showed different preferred orientations. The random oriented film was obtained heat-treatment for pyrolysis below 330℃. The preferred orientations to the direction of the (111) and (100) plane were obtained by heat-treatment for pyrolysis at 330℃ and 350℃, respectively. FTIR spectroscopy was used to detect the remanent organic materials in the thin films prior to the final heat treatment. The stress in the dreied films was measured using Thin Film Stress Measuring Apparatus. The preferred orientation of the PZT thin films were observed using X-ray diffraction analysis (XRD), glancing angle X-ray diffraction and texture coefficient calculation. The micro- structure and selected area diffraction pattern of the PZT thin films were also investigated using scanning electron microscopy (SEM) and transimission electron microscopy (TEM), respectively. The change of orientation with drying temperature for pyrolysis was explained by the relation between the amount of asymmetric stretching COO in the dried thin films and the Pt-Ti intermetallic compounds formed in the bottom electrode.
The hysteresis loop, the fatigue and the capacitance-voltage characteristics of the films having different orientations were investigated using a standardized ferroelectric test system. The dielectric constant characteristics of the films was investigated using an impedance analyzer. The pyroelectric coefficient and the current-voltage were investigated using a pA meter. The piezoelectric coefficient was investigated using a nanovoltermeter. The (100) oriented film showed relatively high dielectric constant compared to the (111) and the randomly oriented films. The films oriented in particular directions showed higher hysteresis parameters than the randomly oriented film. In the current density-electric field characteristics, the (100), the (111) and the randomly oriented films showed three regions having different slopes. The leakage current densities of the films oriented in particular directions were lower than that of the randomly oriented film. The pyroelectric ciefficient of the (100) oriented film was higher than that of (111) and the randomly oriented films after poling process.
